YES O(n^5) TRS: { i(0()) -> 0(), i(i(x)) -> x, i(+(x, y)) -> +(i(x), i(y)), +(x, 0()) -> x, +(x, i(x)) -> 0(), +(x, +(y, z)) -> +(+(x, y), z), +(0(), y) -> y, +(i(x), x) -> 0(), +(+(x, y), i(y)) -> x, +(+(x, i(y)), y) -> x } DUP: We consider a non-duplicating system. Trs: { i(0()) -> 0(), i(i(x)) -> x, i(+(x, y)) -> +(i(x), i(y)), +(x, 0()) -> x, +(x, i(x)) -> 0(), +(x, +(y, z)) -> +(+(x, y), z), +(0(), y) -> y, +(i(x), x) -> 0(), +(+(x, y), i(y)) -> x, +(+(x, i(y)), y) -> x } Matrix Interpretation: Interpretation class: triangular [X9] [X4] [1 0 0 0 0][X9] [1 1 0 1 0][X4] [1] [X8] [X3] [0 1 0 0 0][X8] [0 1 0 1 0][X3] [1] [+]([X7], [X2]) = [0 0 1 0 0][X7] + [0 0 1 1 0][X2] + [1] [X6] [X1] [0 0 0 1 0][X6] [0 0 0 1 0][X1] [0] [X5] [X0] [0 0 0 0 1][X5] [0 0 0 0 1][X0] [0] [X4] [1 1 1 1 0][X4] [1] [X3] [0 1 0 0 0][X3] [0] [i]([X2]) = [0 0 1 0 0][X2] + [0] [X1] [0 0 0 1 0][X1] [0] [X0] [0 0 0 0 1][X0] [0] [0] [0] [0] = [0] [0] [0] Qed